High-performance Photoanodes Research Articles

Creating an intermediate energy band to boost the photoelectrochemical efficiency of TiO2 for solar-driven hydrogen production

The utilization of photoelectrochemical processes for hydrogen generation from water and solar energy offers a promising avenue to replace non-renewable energy sources. Nevertheless, achieving high-performance photoanode electrodes poses a significant challenge. In this study, we present the synthesis cerium and chromium-doped TiO2 (CeCrTiO2) is produced through a simple, scalable, and cost-effective hydrothermal method on a fluorine-doped tin oxide (FTO) substrate. the introduction of Ce and Cr impurities is highlighted for its role in creating an impurity band within CeCrTiO2. This impurity band is instrumental in enhancing the separation and movement of electrons and holes, contributing to the improved performance of CeCrTiO2 as a photoanode in photoelectrochemical applications. Hence, the photocurrent density value of CeCrTiO2 is 4.5 times higher than that of bare TiO2. This suggests that CeCrTiO2 exhibits improved efficiency in generating a photocurrent when exposed to light, indicating enhanced photoelectrochemical performance. The amount of hydrogen produced by CeCrTiO2 is noted to be 4.88 times greater than that of bare TiO2. This highlights the material's effectiveness in harnessing solar energy to drive the water-splitting reaction, leading to a higher yield of hydrogen gas. The synthesis of CeCrTiO2 through a hydrothermal method results in a photoanode with significantly enhanced performance, positioning it as a promising candidate for advancing photoelectrochemical processes aimed at replacing non-renewable energy sources.

Elucidating the dynamics and transfer pathways of photogenerated charge carriers in V2O5/BiVO4 heterojunction photoanodes: A transient absorption spectroscopy study

Pairing of bismuth vanadate (BiVO4) with vanadium pentoxide (V2O5) forms a Type II heterojunction photoanode, which has been proven to be a high-performance photoanode architecture for efficient photoelectrochemical (PEC) water oxidation. To further support for advanced rational design and improvement of the heterojunction photoanode, it is quintessential to understand the mechanics and properties of photogenerated charge carriers formed. This study aims to probe the dynamics of photogenerated electron-hole pairs formed in pristine photoanode as well as the heterojunction photoanodes using transient absorption spectroscopy (TAS). Relative to the BiVO4/V2O5 structure, modelling and quantification of the decay constant helps in explaining why the V2O5/BiVO4 heterojunction photoanode exhibited a longer lifetime of the photogenerated charge carriers with a lower decay rate constant that leads to a much-improved overall generation of photocurrent density. An oxygen evolving catalyst of nickel oxyhydroxide (NiOOH) was then anchored on the exterior surfaces of the heterojunction photoanode system to further investigate and modify the transfer pathways of the photogenerated charge carriers. Furthermore, the hole- and scavenger-assisted TAS measurements on the BiVO4/V2O5 heterojunction photoanode revealed that the majority of trapped holes species are accumulated within the BiVO4 layer. The findings suggested that the Type II heterojunction formation in V2O5/BiVO4 could effectively reduce its charge recombination process.

Coupling multifunctional ZnCoAl-layered double hydroxides on Ti-Fe2O3 photoanode for efficient photoelectrochemical water oxidation

The efficiency of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of the oxygen evolution reaction (OER). This study developed a composite photoanode for water oxidation by incorporating ternary LDHs (ZnCoAl-LDH) onto Ti-Fe2O3 as a cocatalyst. The ZnCoAl-LDH/Ti–Fe2O3 photoanode achieved a photocurrent density of 3.51 mA/cm2 at 1.23 V vs. RHE, which is 9.8 times higher than that of bare Ti-Fe2O3. Through a series of characterizations, the synergistic effects among the three metals were revealed. Furthermore, the addition of Zn can induce the formation of more high-valent Co, increasing the conductivity of CoAl-LDH and significantly reducing the surface charge transfer resistance. These advantages significantly enhance the injection efficiency of ZnCoAl-LDH/Ti-Fe2O3 (82 %), thereby accelerating the OER kinetics of Ti-Fe2O3. Our work introduces new approaches for selecting photoelectrochemical cocatalysts and designing high-performance photoanodes for water splitting.

One-Step Self-Assembled WO3/rGO Microspheres Photoanode Assembled Efficient Photocatalytic Fuel Cells for Simultaneous Organic Pollutant Degradation and Electricity Generation.

Photocatalytic fuel cells (PFCs) present a promising and environmentally friendly approach to simultaneously treat organic pollutants in wastewater and electricity generation. The development of photoanodes with high light absorption and carrier mobility is essential for enhancing the performance of PFCs but remains challenging. Herein, a one-step self-assembly strategy was adopted to develop flower-like WO3/rGO microspheres for PFC devices. Attributed to the abundant surface-active sites, enhanced light harvesting, and efficient separation of photogenerated charge carriers, the WO3/rGO photoanode demonstrated superior rhodamine B (RhB) degradation rate (90% in 2 h), maximum power density (4.74 μW/cm2), and maximum photocurrent density (0.096 mA/cm2), 1.4, 2.4, and 4.0 times higher than the corresponding pure WO3 photoanode, respectively. Density functional theory (DFT) calculations reveal that the built-in electric field formed between the interface of WO3 and rGO promotes the transfer of photogenerated electrons from WO3 to rGO, thus exerting a significant impact on improving the migration and separation of photoinduced charge carriers. Moreover, by combining experimental and theoretical results, a complete PFC operation mechanism for the PFC system was proposed. This study focuses on the strategy of constructing rGO-doped photocatalysts to enhance the interfacial charge transfer mechanism, providing a promising approach for the development of high-performance photoanodes in PFC systems.

Elaboration, Structural and Optical Characterization of the New Ternary Chalcogenide SnSb<sub>2</sub>S<sub>5</sub>

In this study, -antimony sulfide (SnSb2S5) thin films with 200 nm, 312 nm, and 431 nm thicknesses were successfully fabricated using thermal evaporation. These films' structural, optical, and photoanode properties were meticulously characterized to assess their suitability for photovoltaic applications. X-ray diffraction (XRD) analysis confirmed the presence of an orthorhombic symmetry phase within the <em>Pnma</em> space group, ensuring the crystalline quality of the films. Raman spectroscopy further validated the crystal structure and provided detailed identification of the vibrational active modes specific to this pseudo-binary chalcogenide compound. Optical characterization revealed that the SnSb<sub>2</sub>S<sub>5</sub> thin films possess direct optical bandgap energies ranging from 1.91 to 1.99 eV, making them ideal for efficient light absorption in photovoltaic devices. The refractive index (n) displayed minimal variation within the absorption region, indicating stable optical properties. At the same time, it increased proportionally with film thickness outside the absorption region, suggesting enhanced optical behavior with thicker films. This characteristic is particularly advantageous for improving the efficiency of photoanode materials. The combination of favorable structural properties, optimal bandgap energies, and tunable optical responses positions SnSb<sub>2</sub>S<sub>5</sub> thin films as promising candidates for advanced photovoltaic and optoelectronic applications. These findings highlight the potential of SnSb<sub>2</sub>S<sub>5</sub> in developing high-performance photoanodes, contributing to the advancement of solar energy conversion technologies.

Urchin-like Bi2S3 modified TiO2 for improved photocathodic protection of 304SS

Severe charge recombination and poor light absorbance are the limiting factors for TiO2 to access efficient photocathodic protection (PCP) towards metals. Engineering the TiO2 with Bi2S3 to form the heterojunction is proposed to overcome these limitations. Impressively, the optimal Bi2S3-12 h@TiO2 photoanode coupled with 304SS displays an open circuit potential that negatively shifts to −480 mV vs Ag/AgCl, accompanied by a photoinduced current of 18.5μA/cm2. Comprehensively, characterizations discover that a tight interface between TiO2 and Bi2S3 exhibits strong electron interaction. The resulting enhanced PCP performance is attributed to extending the photoresponse range, increasing the carrier density, and improving the photocarrier separation. This work proves and validates the effectiveness of Bi2S3@TiO2 in enhancing the PCP performance and provides the instruction to construct a high-performance photoanode.

Strategic band alignment of zinc oxide photoanode with fibrous silica framework for enhanced photoelectrochemical water splitting efficiency

The urgent need to address both energy demand and environmental concerns has led to the exploration of solar energy utilization in photoelectrochemical (PEC) water splitting. The novelty of fibrous silica zinc oxide photoanode (FSZn) was introduced in this groundbreaking study, synthesized using the meticulous microemulsion method. Our investigation reveals the exceptional properties of FSZn using a comprehensive range of analytical techniques, including FESEM, FTIR, XRD, UV–Vis/DRS TEM, and N2 adsorption–desorption tests. The distinctive features of FSZn arise from its intricate bicontinuous concentric lamellar structure, resulting in a narrow bandgap and a vast surface area. Notably, FSZn exhibits a remarkable photocurrent density of 17.88 mA/cm2, surpassing that of conventional ZnO, which only yields 6.28 mA/cm2. Furthermore, FSZn achieves an impressive solar-to-hydrogen (STH) efficiency of 22.0 %. The favourable alignment of FSZn’s conduction band with the hydrogen reduction potential, which facilitates swift and efficient charge transfer processes conducive to spontaneous hydrogen generation, is responsible for this remarkable performance. The successful development of FSZn represents a significant milestone, offering valuable insights for advancing high-performance photoanodes. By significantly enhancing the efficiency of photoanodes in PEC water splitting processes, FSZn holds promise for accelerating the transition towards sustainable energy solutions.

CoNi2S4 cocatalyst modified TiO2 nanorods/nanoflower homojunction for efficient photoelectrochemical water splitting

Photoelectrochemical water splitting is a promising green method for obtaining clean energy, and its core lies in the preparation of high-performance photoanodes. In this study, TiO2 nanorods/nanoflower homojunction photoanodes were prepared using a one-step hydrothermal method, unlike the complex material composite process used in most previous research works, the TiO2 homojunction photoanode obtained through a one-step method combines the advantages of nanorod and nanoflower structures. CoNi2S4 was further used as an oxygen evolution cocatalyst supported on the TiO2 nanorods/nanoflower homojunction photoanodes, enhancing oxygen evolution kinetics. The photogenerated current density of the obtained TiO2 flower-rod/CoNi2S4 composite photoanode at 1.23 V (versus RHE) was 1.64 mA cm−2, which is 2.3 times of that of TiO2 nanorod photoanode. By density function theory calculation, it is confirmed that the loading of CoNi2S4 cocatalyst can significantly reduce the overpotential and enhance the kinetic process of oxygen evolution reaction.

Ultrasound Induces Local Disorder of FeOOH on CdIn2S4 Photoanode for High Efficiency Photoelectrochemical Water Oxidation.

The regulation of the crystal structure of oxygen evolution cocatalyst (OEC) is a promising strategy for enhancing the photoelectrochemical efficiency of photoanodes. However, the prevailing regulating approach typically requires a multistep procedure, presenting a significant challenge for maintaining the structural integrity and performance of the photoanode. Herein, FeOOH with a local disordered structure is directly grown on a CdIn2S4 (CIS) photoanode via a simple and mild sonochemical approach. By modulating the localized supersaturation of Ni ions, ultrasonic cavitation induces Ni ions to participate in the nucleation and growth of FeOOH clusters to cause local disorder of FeOOH. Consequently, the local disordered FeOOH facilitates the exposure of additional active sites, boosting OER kinetics and extending charge carrier lifetimes. Finally, the optimal photoanode reaches 4.52mAcm-2 at 1.23VRHE, and the onset potential shifts negatively by 330mV, exhibiting excellent performance compared with that of other metal sulfide-based photoelectrodes reported thus far. This work provides a mild and controllable sonochemical method for regulating the phase structure of OECs to construct high-performance photoanodes.

Boosting photoelectrochemical water oxidation by self-assembled Co@β-cyclodextrin supramolecules modified on BiVO4 photoanode

Severe charge recombination and poor surface water oxidation kinetics are key restrictions of BiVO4 photoanode for efficient photoelectrochemical (PEC) water oxidation. In order to overcome this issue, we introduce Co@β-cyclodextrin (Co@β-CD) supramolecule as oxidation evolution catalyst (OEC) into BiVO4 photoanode for the first time via a facile two-step immersion method. The optimal Co@β-CD/BiVO4 photoanode displays a remarkable photocurrent density of 5.3 mA cm−2 at 1.23 VRHE, which is ca. 3.5 times as high as that of pristine BiVO4 photoanode. Further analyses indicate that photogenerated holes could quickly transfer from BiVO4 to Co sites through β-CD, thereby suppressing charge recombination. Moreover, due to the spatial confinement effect of β-CD, the dispersed Co sites in Co@β-CD are considered to possess the high catalytic activity in similar with single-atom catalyst, which accelerates the surface water oxidation kinetics. This work not only demonstrates the superiority of supramolecule/semiconductor composite photoanode, but also provides a facile preparation route for the large-scale preparation of high-performance photoanodes.

Electronic metal-support interaction-induced space charge polarization for boosting photoelectrochemical water splitting

Overcoming the inherent transportation of charge constraint of the photoanode has been critical for seeking feasible photoelectrochemical (PEC) water splitting. Here, we propose to utilize electron metal-support interactions (EMSI) between Cu nanoparticles (NPs) and N-C support for modifying the electronic structure of CuNPs-N-C/SnS2 photoanode and analyze the impact of EMSI on the process of PEC water splitting. The combination of detailed theoretical simulation calculations and comprehensive characterizations indicates that the charge imbalance induced by EMSI within the CuNPs-N-C and SnS2 interfaces results in an enhanced interfacial polarized electric field and boosts the separation of photo-induced carriers at the CuNPs-N-C and SnS2 interfaces. The optimal CuNPs-N-C/SnS2 photoanode displays remarkable properties with a considerably upgraded photocurrent of 2.33 mA cm−2 at 1.23 VRHE, which is 6.30 beyond the value of SnS2 (0.37 mA cm−2). This work paves a way to developing high-performance photoanodes for efficient PEC water splitting.

Enhanced Photoelectrochemical Performance Using Cobalt-Catalyst-Loaded PVD/RF-Engineered WO3 Photoelectrodes

Critical to boosting photoelectrochemical (PEC) performance is improving visible light absorption, accelerating carrier separation, and reducing electron–hole pair recombination. In this investigation, the PVD/RF method was employed to fabricate WO3 thin films that were subsequently treated using the surface treatment process, and the film surface was modified by introducing varying concentrations of cobalt nanoparticles, a non-noble metal, as an effective Co catalyst. The results show that the impact of loaded cobalt nanoparticles on the film surface can explain the extended absorption spectrum of visible light, efficiently capturing photogenerated electrons. This leads to an increased concentration of charge carriers, promoting a faster rate of carrier separation and enhancing interface charge transfer efficiency. Compared with a pristine WO3 thin film photoanode, the photocurrent of the as-prepared Co/WO3 films shows a higher PEC activity, with more than a one-fold increase in photocurrent density from 1.020 mA/cm2 to 1.485 mA/cm2 under simulated solar radiation. The phase, crystallinity, and surface of the prepared films were analysed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The PVD/RF method, scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM) were employed to assess the surface morphology of the fabricated film electrode. Optical properties were studied using UV–vis absorbance spectroscopy. Simultaneously, the photoelectrochemical properties of both films were evaluated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). These results offer a valuable reference for designing high-performance photoanodes on a large scale for photoelectrochemical (PEC) applications.

Sequential doping strategy in rutile TiO2 nanorod for high performance photoanode

Clean hydrogen production technologies are in high demand as an alternative to fossil fuels in order to achieve a carbon–neutral society. One promising approach is photoelectrochemical water splitting, which uses sunlight as an energy source to produce hydrogen. In this study, we propose a strategy for achieving highly efficient photoelectrochemical performance in TiO2 nanorods without the need for additional heterojunction or catalyst reactions. We introduce the plasma-assisted sequential doping process using H and F species to demonstrate highly efficient photoanode for water splitting. In the first stage, hydrogenated TiO2 generated oxygen vacancies and interstitial H in the TiO2 lattice structure, and in the second stage, fluorinated TiO2 exhibited a sequentially cured reaction of oxygen vacancy resulting in enhanced photoelectrochemical performance. Furthermore, theoretical simulations revealed that the sequential doping process induced a stabilized reaction in F compared to direct doping without H plasma doping. This sequential doping strategy can be applied to a wide range of materials and applications, not just to enhance photoelectrochemical devices.

Nanostructured Fe2TiO5 photoanode with enhanced photoelectrochemical water splitting performance by Zn2+ doping and FeNi(OH)x cocatalyst deposition

Combining heteroatom doping and cocatalyst deposition by facile electrospray offers an effective strategy for developing high performance photoanode.

Effect of aging times of fibrous silica cadmium sulfide photoanodes for enhanced photoelectrochemical water splitting

The use of photoelectrochemical (PEC) water splitting to produce hydrogen from solar sources is an alluring potential address to the world’s energy and environmental problems. Cadmium Sulfide (CdS) is a potentially visible light response photoanode of PEC water splitting, but practical use remains a significant barrier due to its low charge carrier separation efficiency. To address this disadvantage, modifications to the morphology of CdS is necessary. Herein, fibrous silica cadmium sulfide (FSCdS) photoanode for PEC water splitting was synthesized using microemulsion method reported in this study. In this study, it will be focused on the effect of aging times which is 6 hours and 8 hours on the structure of FSCdS towards the PEC water splitting. The physicochemical and electrical properties of the photoanodes were investigated using XRD, UV-Vis DRS, FTIR and EIS Nyquist Plot. FSCdS-6H had a higher photocurrent density of 22.1 mA/cm2 at 1.23 VRHE and a higher solar-to-hydrogen (STH) efficiency of 27.2% when compared to FSCdS-8H with 13.0 mA/cm2 and STH of 16.0%. This is due to the better crystallinity, higher Si-Cd-S interaction, and lower electron hole recombination rate of FSCdS-6H photoanode. Fabrication of fibrous silica-based photoanodes revealed significant insight for the creation of highperformance photoanodes for improved PEC water splitting performance.

Solid-state magic: How Bi2O3 and V2O5 combine to create a high-performance photoanode for water oxidation

A simple method to create a BiVO4–V2O5 photoanode with excellent interfacial contact and self-doping with V4+ and oxygen vacancies was proposed in this study. Direct generation of BiVO4 within the film through a solid state reaction between Bi2O3 and V2O5 was achieved, resulting in a highly efficient charge separation and a photocurrent density of 6.6 mA cm−2 at 1.23 V vs. RHE. The bulk charge separation efficiency was 95 %. This study highlights the importance of good interfacial contact for suppressing charge recombination and enabling efficient water oxidation. The developed synthesis method can be a practical approach for fabricating advanced photoelectrodes for sustainable water-splitting technologies, enabling carbon-free fuel production.

High-efficiency entangled hierarchical GaN nanowire-based photoanode for solar-driven water splitting

In spite of significant endeavors aimed at augmenting the solar-to-hydrogen conversion efficiency of GaN-based photoanodes, further strides are imperative to unlock the full potential of GaN as a promising photoanode material. Within this article, we unveil the utilization of entangled hierarchical GaN nanowires (EHNWs) as high-performance photoanodes for efficient solar-driven water splitting, culminating in hydrogen generation. The strategy entails the passivation of GaN nanowires with ZnO overlayers, synergistically supported by an efficient co-catalyst endowed with visible-range light absorption capabilities. The results underscore the promising viability of this approach in the quest for sustainable hydrogen production through solar energy utilization. The growth of EHNWs-based nanostructures engenders an expanded active surface area, bolstering photocatalytic activity, and expediting proficient charge transportation. The amelioration of surface defects and the broadening of the photo absorption spectrum in the visible domain collectively confer a significant enhancement in photocurrent density, reaching up to 3 mA cm−2 which is ∼5 times higher as compared to bare EHNWs. Remarkably, the achieved solar-to-hydrogen conversion efficiency of 4.7 % stands amongst the upper echelons of reported values for GaN-based photoelectrodes cultivated via metal–organic chemical vapor deposition (MOCVD).

Heterojunction of TiO2 nanotubes arrays/Bi2Se3 quantum dots as an effective and stable photoanode for photoelectrochemical H2 generation

The use of semiconductor materials to split water through photoelectrochemical (PEC) processes is a remarkable technique that can transform solar energy into chemical energy, such as H2, in one step. For enhanced H2 generation, efficient separation of electron–hole (e−/h+) pairs and high photogenerated electron conductivity are required for photoanode substrates. In this study, an effective type II heterojunction between Bi2Se3 quantum dots (QDs) and TiO2 nanotube arrays (TNTAs) was constructed by depositing Bi2Se3 QDs on the TNTAs surface. The performance for PEC H2 generation was also investigated. The TNTAs/Bi2Se3 QDs demonstrated the highest photocurrent density of 1.75 mA cm−2, which is 3.8 times greater than bare TNTAs (0.46 mA cm−2) at 1.23 V vs. RHE. They also achieved a high hydrogen generation quantity of 355.8 μmol after 5 h, which is 3.3 times greater than bare TNTAs (105.3 μmol) at 1.23 V vs. RHE. TNTAs and TNTAs/Bi2Se3 QDs photoanodes both exhibited excellent stability for over 7 h. Compared with bare TNTAs, the TNTAs/Bi2Se3 QDs photoanode demonstrated a higher incident photon-to-current conversion efficiency (IPCE) in the UV region and expanded the light response to the visible region due to its lower charge recombination and larger visible light absorption. The exceptional performance of the TNTAs/Bi2Se3 QDs photoanode is due to its proper bandgap energy, which improves the visible light absorption, and its effective charge carrier transfer, which alleviates the recombination of e−/h+ pairs. The modification of TNTAs with Bi2Se3 QDs as a promising metal chalcogenide for improving visible light absorption and PEC water splitting performance has not yet been studied. Therefore, this work paves the way for a facile approach to construct a stable and high-performance photoanode for PEC H2 generation.

BiVO4/boron-doped diamond heterojunction photoanode with boron doping engineering and enhanced photoelectrocatalytic activity

Photoelectrocatalysis is one of the most promising strategies to address ever-growing wastewater problems. A novel heterojunction photoanode formed by depositing a photocatalyst on a boron-doped diamond (BDD) layer has been considered an ideal material for the practical application of photoelectrocatalytic (PEC) degradation due to its advantages of light responsiveness, excellent charge transport, and robustness. In this study, various BiVO4/BDD heterojunction photoanodes with different diamond crystalline qualities and electrical conductivities were successfully fabricated by tuning the boron (B) doping concentration of the BDD layer. It was proposed that the charge transport efficiency of the photoanodes is promoted by optimizing the crystalline qualities and electrical conductivities of BDD films, thereby enhancing the PEC activity of the BiVO4/BDD heterojunction photoanode. Our results suggested that the electrical conductivity of BDD increased and the crystalline quality of BDD deteriorated with increasing B doping concentration. As a result, the PEC activity of the BiVO4/BDD heterojunction photoanode first increased and then decreased. The optimal PEC activity of the BiVO4/BDD heterojunction photoanode was achieved corresponding to the [B]/[C] gas ratio at 500 ppm, producing a current density of 3.3 mA/cm2 at 1.6 VRHE (the potential versus a reversible hydrogen electrode) in 0.1 M Na2SO4 under AM 1.5 irradiation, which was 1.7 times (1.9 mA/cm2) that of the photoanode with a [B]/[C] gas ratio of 3000 ppm. Meanwhile, the optimized tetracycline hydrochloride (TCH) degradation efficiency was 63.5 % within 9 min (500 ppm gas phase), which was 2.5 times (25.1 %) that of the highly doped photoanode with a [B]/[C] gas ratio of 3000 ppm. This study revealed that the excellent PEC performance benefited from the high crystalline quality and high electrical conductivity of BDD, which depended on the optimized B doping concentration. The idea of enhancing the PEC activity of the photoanode by optimizing the properties of the conductive electrode material proposed in this study provides a conceptual reference for fabricating potential high-performance photoanodes in the future.

Commercial-scale reproducible GaN nanowires with 6.4% solar to hydrogen conversion efficiency in photoelectrochemical water splitting

In this article, we demonstrate how commercial-scale reproducible GaN nanowires (GNWs) passivated with metal oxide overlayers and assisted by an efficient co-catalyst with a visible absorption wavelength can be used as a high-performance photoanode for photoelectrochemical (PEC) water splitting to produce solar-driven hydrogen. The facile growth of GNWs using a vapor-liquid-solid method by metal-organic chemical vapor deposition (MOCVD) raises the density of the NWs, increasing the active area for the water splitting reaction and facilitating charge transport. The passivation of surface defects through overlayers and being aided by a co-catalyst with a photo absorption range in the visible region greatly increases the photocurrent density up to 4.6 mA/cm2 under 1 sun illumination at zero applied biasing versus the reference electrode. The measured solar to hydrogen conversion efficiency of 6.4% is among the highest documented values for GNWs-based photoanodes grown using MOCVD.